Blast attenuating containers

ABSTRACT

An aircraft cargo container adapted to provide blast attenuation in the event of an explosion within the container comprises panels (2,3) of blast resistant material joined together by joint means (4,5) which are adapted to provide a relatively rigid joint udner normal handling conditions, but which provide a relatively flexible hinged joint capable of transmitting tensile loads between the panels under blast conditions. Additional reinforcement may be provided by a lattice of high tensile strength straps 6 substantially surrounding the container.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to blast attenuating containers such as aircraftluggage containers.

2. Discussion of Prior Art

It is known to use blast attenuating materials in the construction ofaircraft luggage containers in order to reduce the effects of the blastfrom a detonating or exploding device within the container. Indeed,Applicant's International Patent Application No. PCT/GB90/01724(International Publication No. WO91/07337) describes such a containerusing blast attenuating materials in accordance with Applicant'sco-pending International Patent Application No.PCT/GB90/01723(International Publication No. WO91/07275). The container described inthe first-mentioned patent application is preferentially weakened toensure that the blast caused by an explosive device within the containeris vented in a predetermined direction in order to limit the damagecaused.

An alternative approach, which relies to some extent on the expectationthat only relatively small-scale explosive devices will escape detectionby routine security screening procedures, is to endeavour tosubstantially contain the blast, and fragments from it, within thecontainer.

In either case, it is important to ensure that the parts of thecontainer, if any, which are not preferentially weakened retain a degreeof structural integrity throughout the blast in order to perform thedesired blast absorbing and attenuating function.

Most aircraft containers in current use are of standardisedconstruction, conforming to one or other of the International AirTransport Association's (IATA) specifications for Unit Load Devices.Such containers typically comprise a number of panels assembled on arigid base and joined at their edges to form an enclosure. Whilstcapable of withstanding normal handling loads, the panels and joints arenot capable of effectively containing or attenuating a blast from anexplosive device.

SUMMARY OF THE INVENTION

According to the present invention, a blast attenuating containercomprises a number of panels, at least one of which has blastattenuating properties, the panels being joined together to form anenclosure by joint means which provide a relatively rigid joint betweenthe panels under normal handling loads, but which provide a relativelyflexible hinged joint capable of transmitting tensile loads between thepanels under blast conditions.

The invention derives from the recognition that in order to effectivelyattenuate and hopefully contain the blast from a bomb detonating withinthe enclosure, it is important that the container, at least in thoseparts which are not preferentially weakened, substantially retains itsstructural integrity during the blast to the extent that no majordisintegration or rupture occurs that would allow significant blastpressure to escape.

Conventional joints between container panels necessary to provide thedesired rigid structure for normal handling would either fracture orcause the panel to tear or rupture adjacent the joints under blastconditions. In a container in accordance with the present invention, byensuring that the joint means behave as flexibly hinged tensileload-bearing joints between the panels under such blast conditions, therisk of rupture is considerably reduced thereby also enabling the blastattenuating properties of the panels to be fully effective.

The joint means, which will normally comprise a combination of edge andcorner joints, may be of two different materials, one having the desiredstiffness to provide a rigid joint under normal handling conditions butwhich ruptures or fractures under blast conditions, and the othermaterial having the desired flexible and tensile load-bearingproperties.

Alternatively, the joint means may comprise a single material whicheither inherently exhibits the necessary properties, or whose rigidityunder normal handling conditions is provided by a structural elementwhich deforms or ruptures under blast conditions to leave a flexibletensile load-bearing joint element.

Where the joint means comprise a combination of edge and corner joints,these are preferably connected to one another in a manner which providesa stiff joint between them having the desired rigidity under normalhandling conditions, but which behaves as a flexible tensile-loadbearing joint under blast conditions thereby further reducing the riskof disintegration.

To further improve the blast attenuating properties of the container, itmay be partially completely enclosed within a lattice of high tensilestrength straps which function in the manner of a `string bag` underload conditions again with a view to reducing the risk of disintegrationof the blast containing portions of the container.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in greater detail by of example onlywith reference to the accompanying drawings, of which:

FIG. 1 is a perspective side elevation of an embodiment of the presentinvention in the form of an aircraft luggage container;

FIG. 2 is a sectional view through part of the base of the container;

FIGS. 3 and 4 show schematic sectional view of two different forms ofblast attenuating panel for use in the aircraft luggage container;

FIG. 5 shows a schematic sectional view of part of the base of thecontainer;

FIGS. 6 to 13 show cross-sectional views through different forms ofpanel edge joints for use in the container;

FIGS. 14 and 15 show different forms of corner joint for use in thecontainer;

FIG. 16 illustrates an alternative form of door construction for thecontainer.

DETAILED DISCUSSION OF PREFERRED EMBODIMENT

Referring to the drawings, FIG. 1 shows an aircraft luggage containerconfigured and constructed of lightweight materials to comply with therequirements of the International Air Transport Association's (IATA)Unit Load Device Technical Manual, and essentially comprising a strongrigid base 1, the sides, ends and top of the container being provided bypanels of blast attenuating material (of which only one side panel 2 andone end panel 3 can be seen in FIG. 1) which are assembled on the base 1and joined together by edge joints 4 and corner joints 5 to form asubstantially rigid enclosure.

A loading entrance 7 is provided on one side of the container whichentrance is closed by a door 8 comprising first and second door sections9, 10. The first upper door section 9 is hinged along its top edge toone of the container edge joints 4, and along its lower edge to thesecond door section 10.

The door sections 9, 10 are formed of the same blast attenuatingmaterials as the blast attenuating panels 2, 3 of the container whichwill be described in more detail below, and is provided with suitabledoor closure means (not shown) which are capable of transmitting tensileloads between the door and the base and edge joints surrounding theloading entrance.

Except for the base 1 and loading entrance 7, the container issurrounded by a lattice of woven straps 6 of high tensile strength whichare anchored at various points around the base and loading entrance 7 asshown. The straps 6 may additionally be secured across the door 8 afterit is closed to provide further support both during normal handling andunder blast conditions.

Referring now to FIG. 2, the base 1 comprises a substantiallyrectangular rigid composite panel 11 adhesively bonded around its edgesto a flange 12 projecting inwardly from a surrounding frame 13 ofextruded aluminium. The frame 13 is also formed with an outwardlyprojecting flange 14 adapted to interlock with industry standard floorretaining means in an aircraft luggage compartment, and a recessedchannel 16 which provides external anchor points for the straps 6.

The upper free edge of the frame 13 is formed with a channel 17 intowhich the lower edges of the blast attenuating side and end panels 2, 3of the container are received. These panels 2, 3 may either bepositively retained within the channel solely by the straps 6, althoughpreferably they are secured either by adhesive bonding or, as shown, bymechanical retaining means. In this embodiment, the mechanical retainingmeans comprises a `C`--section resilient spring strip 18 press-fittedbetween cooperating recesses 19, 20 along the lower inside edge of thepanel 2 and the adjacent internal surface of the channel 17respectively. The other internal surface of the channel 17 is formedwith a ridge 21 to provide a more secure friction fit for the panel 2within the channel 17. In use, application of tensile loading betweenthe panel 2 and the base 1 tends to cause the `C`--section spring strip18 to open and thus lock the panel to more securely in the channel 17.Blast pressure acting on the inner lip of the channel 17 providesincreased grip under blast conditions.

The portion 22 of the frame 13 which extends between the flange 12 andthe channel 17 is of curved cross-section presenting a concave internalcorner around the base of the container which serves to deflect theblast by avoiding the concentration of pressure that would otherwiseoccur with an angular corner.

With reference now to FIG. 3, the base panel 11 of the base 1, providingas it does the load-bearing floor of the container, is of lightweightcomposite multi-layer rigid construction designed to have sufficientstrength and rigidity to withstand not only the considerable loadsexperienced during normal use, but also to contain and prevent thetransmission of blast pressures and fragments in the event of anexplosion occurring within the container. It therefore differs from theside and end panels 2, 3 in that it is blast reflecting rather thanblast absorbing or blast attenuating.

The upper and lower surfaces of the panel 1 are provided by layers 25,26 of aluminium, or `E`--glass impregnated with phenolic resin,approximately 2 mm thick. Sandwiched between the two layers 25, 26 is anupper honeycomb layer 27 formed either of extruded aluminium or phenolicresin-impregnated paper such as Nomex (RTM) which is approximately 5 mmthick, and a lower layer 28 of armour plating comprising a layer 30 ofaluminium oxide ceramic approximately 5 mm thick sandwiched between thinrubber sheets 31, 32. Between the honeycomb layer 27 and the armourplating layer 28 is a 2 mm thick layer of aluminium, or `E`--glassimpregnated with phenolic resin, similar to the outer layers 25, 26. Thevarious layers of the sandwich materials comprising the panel 11 areadhesively bonded together using appropriate fire resistant phenolicresins.

The base of the container may be additionally provided with a falsefloor (not shown) defining between it and the floor panel 11 a ventingcavity. In such an embodiment, the false floor is preferentiallyweakened in selected areas such that under blast conditions these areasare ruptured to provide passages through which blast gases can vent intothe venting cavity thereby reducing the internal pressure during anexplosion within the container.

The upper and lower surface layers 25, 26 provide a strong impactresistant skin for the panel 11, the honeycomb layer 27 imparts a highdegree of rigidity whilst the armour plating layer 28 serves primarilyto prevent the transmission of blast fragments through the floor of thecontainer.

The blast attenuating side, end and top panels 2, 3 of the containermaybe of any suitable lightweight blast attentuating material, althoughthey are preferably formed of a composite blast attenuating material inaccordance with the Applicant's International Patent ApplicationNo.PCT/GB90/01723 (International Publication No.WO91/07275). Examples ofsuitable materials designed specifically for use in the presentapplication are shown in FIGS. 4 and 5.

The material shown in FIG. 4 comprises outer layers 35, 36, of impactresistant material and sandwiched between each of these layers 35, 36and intermediate layer 37 are slabs 39 of lightweight foamed or cellularplastics material supported along, and effectively embedding therein,the corrugations of a respective corrugated support layer 40, 41. Thecorrugations of the support layer 40, 41 and of the slabs 39 in each ofthe two main layers of the sandwich are arranged orthogonal to oneanother to provide, in aggregate, a reticulated or cellular crumplepattern under blast conditions.

The various layers of the sandwich structure are adhesively bondedtogether using a fire resistant phenolic resin to provide a unitarystructure having an overall thickness of approximately 35 mm, thethickness of each of the layers 35, 36, 37 being approximately 1.5mm andthe depth of each of the slabs 39 approximately 15mm.

The layers 35, 36, 37 which are air permeable under blast conditions areformed of a glass fibre reinforced material such as woven or stitched`S` or `E` glass fibres impregnated with phenolic resin. Such materialis advantageously non-permeable to air (and water) under normal handlingconditions but becomes porous and permeable under blast conditions whenthe resin is blown from the interstitial holes in the glass fibrestructure. In order to ensure that the interstices between the fibresare filled with resin, a backing tissue (not shown) may be inserted aspart of the skin matrix for layers 35, 36, 37.

The slabs 39 are formed of a foamed phenolic resin which is highlyblast-absorbent as it is crushed to powder under blast conditions. Thecorrugated layers 40, 41 are formed of stitched `E` glass fibresimpregnated with phenolic resin to provide a degree of stiffness whichreinforces the foamed slabs 39 to provide increased energy absorption asthey are compressed under blast conditions.

The material shown in FIG. 5 is generally similar to that shown in FIG.4 (with corresponding parts bearing the same reference numbers) exceptthat the central layer 37 of impact resistant material has been omitted,and the foamed energy-absorbent slabs 39 are formed in situ rather thanbeing pre-formed as in the FIG. 4 embodiment. In a further embodiment,not shown, the corrugated reinforcing layers 40, 41 are of dimpledrather than corrugated construction.

In addition to their inherent blast absorbing properties, the materialsdescribed with reference to FIGS. 4 and 5 also display high tensilestrength as well as a high coefficient of elongation before failurewhich is primarily imparted by the corrugated (or dimpled) reinforcinglayers 40, 41.

In order to provide an effective blast attenuating structure, the blastattenuating panels of the container must be joined together by suitablejoints. In accordance with the present invention, these edge joints,which are referenced 4 in FIG. 1, have relatively high stiffness toprovide a substantially rigid structure under normal handling loads, butessentially behave as flexible hinges capable of transmitting hightensile loads under blast conditions.

A number of suitable edge joints will now be described with reference toFIGS. 6 to 13. Referring first to FIG. 6, the edge joint 50 shown incross-section comprises an elongate structure of composite materialdesigned to connect the edges of two adjacent blast attenuating panels51, 52 of the container at right angles to one another. The joint 50essentially comprises inner and outer parallel webs of material 53, 54,the inner web 53 being substantially wider than the outer web 54, andthe two webs being folded through 90° and are held apart by radiallyextending spacers 55, 56, 57.

Additionally, the joint is formed with an integral deflector plate 58which is provided by a third web extending across the right angle bendof the inner surface of the folded inner web 53. The free edges of thetwo webs 53, 54 define, in conjunction with the radial spacers 55, 57,respective channels 60, 61 adapted to receive the edges of the panels51, 52 which are adhesively bonded therein. The greater widths of theinner web provides it with an increased area of bonding contact witheach of the panels 51, 52.

The joint is formed of a composite material capable of transmittingtensile loads both longitudinally and transversely, and comprises afibre reinforced plastics composite having good rigidity at normalhandling loads under which the deflector plate 58 provides additionalrigidity and support.

However, under blast conditions, the deflector plate 58 serves initiallyto deflect the blast away from the corner thus avoiding concentrationsof blast pressure which would otherwise occur at this point, andsubsequently yields to permit the joint to flex whilst transmittingtensile loads between the adjacent plates 51, 52 as the container tendsto adopt a spherical shape under the pressure of the blast. Thiscritical feature of the invention greatly reduces the risk of rupture ofeither the joint itself or the panels thereby greatly assisting in blastcontainment.

The edge joint shown in FIG. 7 is similar to that shown in FIG. 6 andcorresponding parts bear the same reference numerals. In this embodimentthe centre of the deflector plate 58 is spaced from the centre of thefolded inner web 53 by a radial spacer 59. Note also that the spacer 56is replaced by a pair of spacers 56a, 56b which are thus staggered withrespect to the spacer 59. This construction enhances the blastdeflecting properties of the deflector plate 58.

In both the joints of FIG. 6 and FIG. 7, the hollow spaces providedbetween the webs 53, 54 and 58 can be filled with blast absorbent foamor other material to improve blast absorption.

Referring now to FIG. 8, again the construction of this edge joint issubstantially identical to that described with reference to FIG. 7except that the means for connecting the joint to the panels 51, 52comprises mechanical locking means substantially identical to thatdescribed with reference to FIG. 1 for securing the blast attenuatingpanels of the container to the base 1.

The edge joint shown in FIG. 9, is generally similar in overallconstruction to that described with reference to FIGS. 6 and 7 exceptthat it is made of two separate components 64, 65, the integral outerweb of the main component 65 being supplemented by a separate externalcomponent 64 of different material. In addition, the FIG. 9 embodimentshows a different configuration for the spaces between the webs ofmaterial forming the main component 65 of the joint.

The main component 65 of the joint shown in FIG. 9 is designed toprovide the main longitudinal tensile strength for the joint and is thusformed as a pultruded fibre reinforced plastics composite havinglongitudinal reinforcing fibres. The external component 64 is formed ofa woven or stitched "E" glass fibre mat impregnated with phenolic resinand bonded over the outer surface of the main component 65 and extendinginto bonded contact with the edges of the two panels 51, 52 and isdesigned to provide the main transverse tensile strength for the jointunder blast conditions.

Again, the handling and blast performance characteristics of the jointare substantially as described with reference to FIGS. 6, 7 and 8.

Referring now to FIG. 10, the joint shown comprises a mechanical hinge62 coupled to the plates 51 and 52 by adhesive bonding and encased in acomposite material 63 which provides the joint's rigidity under normalhandling conditions, but which is frangible under blast conditions.

A blast deflector plate 64 is provided across the corner of the jointwhich is formed of `E` or `S` glass fibre reinforced resin which servesnot only to prevent concentration of blast pressure in the corner of thecontainer, but also provides additional rigidity to the joint at normalstrain rates.

The material of the encasement 63 may be of suitable blast absorbentmaterial such as foamed phenolic resin, and similar material may be usedto fill the hollow portions of the joint shown in FIGS. 6 to 9 toprovide additional blast absorption.

Referring now to FIG. 11, the joint comprises curved bearing members 76,77 bonded along the edges of adjacent panels 51, 52 and coupled togetherby opposed hooked tongues 78, 79 formed on the internal surface of ablast deflector plate 80 which is of high elongation material. Thetongues 78, 79 engage within cooperating grooves 81, 82 formed in thebearing members 76, 77 to form a hinged roller joint between the panels51, 52.

The joint is completed by an external component 64 bonded between thepanels 51, 52 in a similar manner to the external component 65 of FIG.10. The inner voids of the joint may be filled with blast absorbent foamor other material to increase rigidity of the joint under normalhandling conditions while providing additional blast absorptionproperties.

In operation under blast conditions the portion of the deflector plate80 between the tongues 78, 79 stretches to allow the joint to hingeabout the curved bearing members 76, 77 whilst retaining the integrityof the joint.

FIG. 12 shows a further form of joint in accordance with the presentinvention which is of unitary construction comprising a high-strengthaluminium or fibre-reinforced composite extrusion 100 of generallyhollow trapezoidal box section formed with fixing flanges 101, 102 alongits length. Other cross-sectional configurations, e.g. circular, maysimilarly be used for the extrusion 100. The face 103 of the box-sectionextrusion which adjoins the two fixing flanges 101, 102 ispreferentially weakened along its length by means of a groove 104.

The fixing flanges 101, 102 are fastened to the edges of blast absorbentpanels 106 (only one shown) by means of mechanical fasteners 107.Adhesive bonding may alternatively or additionally be used. The panel106 is of generally similar construction to those described earlier,e.g. with reference to FIGS. 4 and 5, except that the impact-resistantouter sheets 109, 110 and intermediate reinforcement sheets 108 arebrought together at their edges to facilitate their attachment to thefixing flanges 101, 102, of the joint. It will be apparent that asimilar construction may also be used in conjunction with some or all ofthe joints described with reference to FIGS. 6 to 11.

In operation, the joint provides a rigid edge joint for the containerunder normal handling conditions, but is adapted to rupture along theweakening groove 104 in the event of a blast within the container. Inthis eventuality, the remaining wall portion of the box sectionextrusion then provides a flexible tensile load-bearing joint betweenthe adjoining panels.

FIG. 13 shows a further form of joint construction comprising a pair ofco-operating channel section extrusions 110, 111 of aluminium orfibre-reinforced composite material which are bolted together atperiodic intervals along their length by means of bolts 112. The innerextrusion 110 is, in use, fastened along edge flanges 113, 114 to theedges of blast attenuating panels 115 (only one is shown) by means ofmechanical fasteners 116 (as shown) or adhesive bonding or both in themanner described with reference to FIG. 12.

The outer extrusion 111 is formed along its length with a pair ofweakening grooves 117, 118 adjacent to the angles of the channelsection. Where straps 6 (see FIG. 1) are provided, these pass betweenthe two extrusions 110, 111 so that when the extrusions are boltedtogether, the straps are tensioned.

In operation, the joint again provides rigidity under normal loadhandling conditions, but when subject to a blast within the container,the outer extrusion 111 is designed to break along the weakening grooves117, 118 to provide a flexible tensile load-bearing joint between theadjoining panels 106.

Referring now to FIG. 14, a corner joint suitable for use in conjunctionwith the form of edge joint 50 described with reference to FIG. 6comprises a moulding 66 of composite or other suitable material formedwith three pairs of mutually orthogonal projections 67 which are adaptedto be adhesively bonded into the hollow spaces defined between the webs53, 54 of the joint 50 as shown.

The material for the corner joint moulding is selected such as toprovide under normal handling conditions, a substantially rigid jointbetween the three edge joints to which it is connected, but to behave asa relatively flexible hinged joint between them when subjected to loadsexperienced under blast conditions.

A less rigid material for the corner joint 66 may be chosen where thecorner is provided with an external reinforcing corner plate 69 of `E`or `S` glass fibre adhesively bonded over the corner joint as shown.Alternatively, or preferably additionally, an internal corner deflectorplate (not shown) may also be provided on the interior of each cornerjoint 66 for blast deflection, and to provide addition reinforcement.This is suitably shaped to match the deflector plates 58 on the adjacentedge joints 50.

In the case of the edge joints described with reference to FIGS. 7, 8and 9, corner joints for use with these joints will be of generallysimilar construction to that shown in FIG. 14 but the number andconfiguration of the projections 67 will obviously be varied tocooperate with the particular configuration of the edge joint used.

Also seen in FIG. 14 on the outer surface of the exterior cornerreinforcement plate 69 is a pair of guide brackets 71 for the straps 6shown in FIG. 1. Similar pairs of brackets may be provided at otherpositions on the corner joints and at appropriate intervals along theedge joints to ensure positive location of the straps in use.

Referring now to FIG. 15, this illustrates an alternative form of cornerjoint comprising three end fittings 73 which are adhesively bonded intothe ends of adjacent edge joints 50 in a manner similar to thatdescribed for the corner joint moulding 66 in FIG. 14. The end fittings73 are each formed with an eye through which a tie ring 74 passes toflexibly couple the three fittings together.

The corner joint thus formed may then be encased within a frangiblecomposite material in a fashion similar to that described with referenceto the hinged joint in FIG. 10, and an additional reinforcing plate 75may be adhesively bonded over the exterior of the joint to provideadditional stiffness and protection during handling.

Referring now to FIG. 16, this shows an alternative form of doorconstruction for the opening 7 of the container of FIG. 1. Thiscomprises a series of slats 90 each comprising an elongate blastattenuating panel of similar construction to the blast attenuating sideand end panels 2, 3 of the container described with reference to FIGS. 4and 5. The slats 90 are interlaced with strips of tape 91 bonded to theslats 90 whilst providing a flexible hinged joint between adjacentslats. The tape is of a woven high-tensile strength material, such asnylon, similar to the straps 6 described with reference to FIG. 1.

The door may simply be suspended as a curtain from the joint 4 at thetop of the opening 7 such that it can be opened simply by folding orrolling it upwards. Alternatively it may be mounted in guide channels oneither side of the opening 7 whereby it may be opened by an up-and-oversliding action.

Integrity of the container structure over the doorway is ensured bypositive location of the door material around the periphery of theloading entrance 7.

The operation of the container in accordance with the invention insuppressing the effects of an explosion within the container will now bedescribed.

The primary purpose of the blast attenuation construction is tosubstantially attenuate shock waves and pressures generated by anexplosion to a level which can be accommodated by the aircraftstructures and systems, and also that any fragments escaping from theblast are of low momentum insufficient to cause major damage to theaircraft structure.

When an explosion takes place within the container, there is a veryrapid rise in pressure with resultant shock waves. Typically pressuresof 200 kPa (30 lb/in²) are not uncommon from a device containing a smallamount of plastic explosive.

The blast pressure within the container causes the container structureto deflect and expand towards a spherical shape. In the embodimentdescribed above, the base 1 of the container is rigid andnon-attenuating being designed to resist serious damage to the freightfloor structure of the aircraft, whilst the blast attenuating panels 2,3 of the container provide the primary blast attenuating mechanism.

In this connection, as the structure deforms towards a spherical shape,the blast attenuating panels gradually absorb energy by the progressivedeformation and collapse of the various panel materials substantially asdescribed in Applicant's co-pending International Patent ApplicationNo.PCT/GB 90/01723 referred to above.

The containers and joint means in accordance with the present inventionmay also be used in conjunction with containers in accordance withco-pending International Patent Application No. PCT/GB/92/02379 whichdescribes additional blast absorption mechanisms for use in aircraftcontainers.

In accordance with the invention, the edge and corner joints of thecontainer serve to hold the blast attenuating panels together whilstallowing the structure to freely deform towards a spherical shapethereby enabling the blast attenuating properties of the panels to befully effective. The longer the panels can be held together and deformand expand without rupture the greater will be the attenuation achieved.

In this regard the corrugated layers 40, 41 of the blast attenuatingpanel materials shown in FIGS. 4 and 5 allow high energy absorbingdeformation and expansion of the material before rupture. Theorientation of the corrugation in layers 40, 41 may be linear as shownor in the form of concentric rings to allow ballooning of the panel whensubjected to blast energy.

The outer straps 6, where provided, assist blast attenuation byproviding a tensile resistance to the expansion and deformation of thecontainer structure thus absorbing further energy and preventing ordelaying disintegration of the container. Although the straps are shownin FIG. 1 anchored to the base 1, they may alternatively be wound aroundthe entire periphery of the container in any or all axes and may bepermanently bonded to or integrally formed with the container structureduring production.

We claim:
 1. A blast attenuating container comprising:number of panels,at least one of which has blast attenuating properties, the panels beingjoined together to form an enclosure by joint means for providing arelatively rigid joint between joined panels under normal handling loadsand for providing a relatively flexible hinged joint capable oftransmitting tensile loads between joined panels under blast conditions.2. A blast attenuating container as claimed in claim 1, wherein thejoint means comprise:first and second components, the first componenthaving sufficient stiffness to provide a rigid joint under normalhandling conditions, but which is adapted to rupture or fracture underblast conditions, but which is adapted to rupture or fracture underblast conditions, and the second component providing a flexible tensileload-bearing joint between panels following rupture or fracture of thefirst component.
 3. A blast attenuating container as claimed in claim 2,wherein the second component (62) of the joint is encased within thefirst component (63).
 4. A blast attenuating container as claimed inclaim 2, wherein the second component (62) comprises respective hingemembers rigidly connected to the edges and/or corners of the panels(51,52) and mechanically hinged to one another.
 5. A blast attenuatingcontainer as claimed in claim 1, wherein the joint means (50) is formedof a material which is rigid under normal handling conditions, but whichis rupturable or deformable under blast conditions to provide a flexibletensile load-bearing joint between the panels.
 6. A blast attenuatingcontainer as claimed in claim 5, wherein the joint means is formed ofaluminium or fibre reinforced plastics composite material.
 7. A blastattenuating container as claimed in claim 5, wherein the edge jointmeans (50) comprise a pair of parallel webs (53,54) angled to provide acorner between adjoining panels and spaced apart to provide a gapbetween them, the edges of each web being bonded and/or mechanicallyfastened to the edges of the panels (51,52).
 8. A blast attenuatingcontainer as claimed in claim 7, wherein the angled inner web (53) ofthe joint means (50) if subtended by a third web (58) which providesrigidity for the joint under normal loads but which is adapted torupture under blast conditions such that the angled pair of webs (53,54) provides a flexible tensile load bearing joint between the panels.9. A blast attenuating container as claimed in claim 7, wherein thespace between the webs (53, 54, 58) is filled with blast absorbentmaterial.
 10. A blast attenuating container as claimed in claim 5,wherein the edge joint means (100) comprise an elongate member of hollowsection formed externally along its length with means (101, 102) forattachment to respective panels (106) of the container, a region(103,104) of the hollow section member between the said attachment meansbeing preferentially weakened along the length of the joint such that itruptures under blast conditions, the remaining wall section providing aflexible tensile load bearing joint between the panels.
 11. A blastattenuating container as claimed in claim 1, wherein the panel(s) havingthe blast attenuating properties comprise one or more layers (39) oflightweight crushable or deformable foamed or cellular materialsandwiched between layers of impact resistant material (35, 36, 37). 12.A blast attenuating container as claimed in claim 11, wherein saidlayers of lightweight foamed or cellular material (39) have embeddedtherein corrugated or dimpled reinforcing sheet material (40, 41)adapted to crumple under blast conditions to provide additional blastenergy absorption.
 13. A blast attenuating container as claimed in claim11 wherein said layers of impact resistant material (35, 36, 37) aresubstantially impermeable to air under normal handling conditions, butbecome air permeable under blast conditions.
 14. A blast attenuatingcontainer as claimed in claim 11, wherein the layers of impact resistantmaterial (35, 36, 37) and/or reinforcing sheet material (40, 41) whereincorporated meet at their edges adjoining said joint means tofacilitate attachment thereof to said joint means.
 15. A blastattenuating container as claimed in claim 1 wherein the joint means(100) are attached to the adjoining panels (106) by mechanical fasteningmeans (107) and/or adhesive bonding.
 16. A blast attenuating containeras claimed in claim 1 further reinforced externally by a lattice ofstraps (6) of high tensile strength.
 17. A joint (100) for use injoining panels (106) of a blast attenuating container, characterised inthat the joint comprises a material or has a component (103, 104) whichhas sufficient stiffness to provide a relatively rigid joint between thepanels under normal handling conditions but which is adapted to rupture,fracture or deform under blast conditions such that the joint provides arelatively flexible hinged joint capable of transmitting tensile loadsbetween the panels (106).